Our long-term goal is to generate the information needed to prepare for or prevent the emergence of pandemic influenza viruses. There is particular concern about the possibility that avian influenza (Al) viruses of the H5N1 subtype could cause a pandemic. H5N1 viruses, endemic in domestic poultry in several Asian countries, have caused an alarming number of deaths by crossing from poultry to humans. Eradication, quarantine and vaccination policies have not succeeded in containing the disease, and the virus continues to be an omnipresent pandemic threat. Two mechanisms are contributing to the perpetuation of H5N1 viruses in Asia: their malleability to adapt to multiple animal species and reassert with other influenza viruses and their constant geographic expansion. The list of countries reporting outbreaks of H5N1 HPAI continues to increase despite the 160 million domestic poultry that have died or been culled in Asia to control the spread of the disease. The estimated economic losses to the Asian poultry sector are around $10 billion, threatening the livelihood of millions of people. This unprecedented outbreak of highly pathogenic avian influenza has taken a new twist having spread to migratory wild aquatic birds that could spread the virus to other parts of the world, including North America. This situation requires the development of intervention strategies that could bring the spread of these viruses to a halt. The goal of this R21 proposal is based on the hypothesis that by manipulating the genome of Al viruses, live attenuated vaccines can be prepared that will not only be useful for pandemic preparedness in humans but also for the control of the disease in animals. Our vaccine approach will allow ease of administration, mass vaccination of live attenuated viruses, and discrimination of vaccinated from infected birds, which ultimately will effectively control the spread of the disease. [unreadable] [unreadable] [unreadable]